The present invention relates to an alternating current driven type plasma display device having a characteristic feature in a dielectric material layer and a method for the production thereof.
As an image display device that can be substituted for a currently mainstream cathode ray tube (CRT), flat-screen (flat-panel) display devices are studied in various ways. Such fat-panel display devices include a liquid crystal display (LCD), an electroluminescence display (ELD) and a plasma display device (PDP). Of these, the plasma display device has advantages that it is relatively easy to form a larger screen and attain a wider viewing angle, that it has excellent durability against environmental factors such as temperatures, magnetism, vibrations, etc., and that it has a long lifetime. The plasma display device is therefore expected to be applicable not only to a home-use wall-hung television set but also to a large-sized public information terminal.
In the plasma display device, a voltage is applied to discharge cells having discharge spaces charged with a discharge gas composed of a rare gas, and a fluorescence layer in each discharge cell is excited with ultraviolet ray generated by glow discharge in the discharge gas, to give light emission. That is, each discharge cell is driven according to a principle similar to that of a fluorescent lamp, and generally, the discharge cells are put together on the order of hundreds of thousands to constitute a display screen. The plasma display device is largely classified either as a direct-current driven type (DC type) or an alternating current driven type (to be abbreviated as xe2x80x9cAC typexe2x80x9d hereinafter) according to methods of applying a voltage to the discharge cells. Each type has advantages and disadvantages. The AC plasma display device is suitable for attaining a higher fineness, since separation walls which work to separate the individual discharge cells within a display screen can be formed, for example, in the form of stripes. Further, it has an advantage that electrodes for discharge are less worn out and have a long lifetime since surfaces of the electrodes are covered with a dielectric material layer.
FIG. 7 shows an exploded perspective of part of a typical constitution of an AC plasma display device. This AC plasma display device comes under a so-called tri-electrode type, and glow discharge takes place mainly between a pair of sustain electrodes 12A and 12B. In the AC plasma display device shown in FIG. 7, a first panel (front panel) 10 and a second panel (rear panel) 20 are bonded to each other in their circumferential portions. Light emission from fluorescence layers 24 in the second panel 20 is viewed through the first panel 10.
The first panel 10 comprises a transparent first substrate 11; pairs of the sustain electrodes (first sustain electrodes 12A and second sustain electrodes 12B) composed of a transparent electrically conductive material and formed on the first substrate 11 in the form of stripes; bus electrodes (first bus electrodes 13A and second bus electrodes 13B) composed of a material having a lower electric resistivity than the sustain electrodes 12A and 12B and provided for decreasing the impedance of the sustain electrodes 12A and 12B; a dielectric material layer 14 formed on the first substrate 11, the sustain electrodes 12A and 12B and the bus electrodes 13A and 13B; and a protective layer 115 formed on the dielectric material layer 14. Generally, the dielectric material layer 14 is composed, for example, of a calcined product of a low-melting glass paste, and the protective layer 115 is composed of magnesium oxide (MgO).
The second panel 20 comprises a second substrate 21; second electrodes (also called address electrodes or data electrodes) 22 formed on the second substrate 21 in the form of stripes; a dielectric substance layer 23 formed on the second substrate 21 and the second electrodes 22; insulating separation walls 25 which are formed in regions on the dielectric substance layer 23 and between neighboring second electrodes 22 and which extend in parallel with the second electrodes 22; and fluorescence layers 24 which are formed on, and extend from, upper surfaces of the dielectric substance layer 23 and which are also formed on side walls of the separation walls 25. Each fluorescence layer 24 is constituted of a red fluorescence layer 24R, a green fluorescence layer 24G and a blue fluorescence layer 24B, and the fluorescence layers 24R, 24G and 24B of these colors are formed in a predetermined order. FIG. 7 is an exploded perspective view, and in an actual embodiment, top portions of the separation walls 25 on the second panel side are in contact with the protective layer 115 on the first panel side. A region where a pair of the sustain electrodes 12A and 12B and the second electrode 22 positioned between two separation walls 25 overlap corresponds to a discharge cell. A rare gas is sealed in each space surrounded by neighboring two separation walls 25, the fluorescence layer 24 and the protective layer 115. The first panel 10 and the second panel 20 are bonded to each other in their circumferential portions.
The extending direction of projection image of the bus electrodes 13A and 13B and the extending direction of projection image of the second electrodes 22 make an angle of 90xc2x0, and a region where a pair of the sustain electrodes 12A and 12B and one set of the fluorescence layers 24R, 24G and 24B for emitting light of three primary colors overlap corresponds to one pixel. Since glow discharge takes place between a pair of the sustain electrodes 12A and 12B, a plasma display device of this type is called xe2x80x9csurface discharge typexe2x80x9d. In each discharge cell, the fluorescence layer excited by irradiation with vacuum ultraviolet ray generated by glow discharge in the rare gas emits light of colors characteristic of kinds of fluorescence materials. Vacuum ultraviolet ray having a wavelength depending upon the kind of the sealed rare gas is generated.
FIG. 6 shows a layout of the sustain electrodes 12A and 12B, the bus electrodes 13A and 13B and the separation walls 25 in the plasma display device shown in FIG. 7. A region surrounded by dotted lines corresponds to one pixel. For clearly showing each component, slanting lines are added to FIG. 6. One pixel generally has the form of a square. One pixel is divided into three sections (discharge cells) with the separation walls 25, and light in one of three primary colors (R, G, B) is emitted from one section. FIG. 23 shows a schematic partial end view of the first panel 10 having the above structure when the first panel 10 is cut along an arrow Bxe2x80x94B in FIG. 6.
FIG. 14 schematically shows a variant in which the layout of the sustain electrodes 12A and 12B, the bus electrodes 13A and 13B and the separation walls 25 in the plasma display device is varied. JP-A-9-167565 discloses this variant, which has a structure in which the sustain electrodes 12A and 12B extend from a pair of the bus electrodes 13A and 13B toward the bus electrodes 13B and 13A. When cut in the same direction as the direction of the arrow Bxe2x80x94B in FIG. 6, the first panel 10 having the above structure gives a schematic partial end view as shown in FIG. 23.
Generally, the discharge gas charged in the discharge space consists of a gas mixture of an inert gas such as a neon (Ne) gas, a helium (He) gas or an argon (Ar) gas with approximately 4% by volume of a xenon (Xe) gas, and the gas mixture has a total pressure of approximately 6xc3x97104 Pa to 7xc3x97104 Pa, and the xenon (Xe) gas has a partial pressure of approximately 3xc3x97103 Pa. Further, a pair of the sustain electrodes 12A and 12B has a distance of approximately 100 xcexcm from each other.
The problem with presently commercialized AC plasma display devices is that that the brightness thereof is low. For example, a 42-inch type AC plasma display device has brightness of approximately 500 cd/m2 at the highest. For practically commercializing an AC plasma display device, further, it is required, for example, to attach a sheet or a film as a shield against electromagnetic waves or external light to the outer surface of the first panel 10, and the AC plasma display device tends to be considerably dark on an actual screen.
The first panel 10 of the AC plasma display device has, for example, the dielectric material layer 14 composed of a dielectric material such as a low-melting glass paste. The dielectric material layer 14 is generally formed by a screen printing method. When the AC plasma display device is driven, the dielectric material layer 14 is allowed to accumulate a charge, and an oppositexe2x88x92directional voltage is applied to the sustain electrodes to discharge the accumulated charge, whereby plasma is generated. The brightness depends upon the quantity of vacuum ultraviolet ray generated from the plasma. For improving the brightness, therefore, it is required to allow the dielectric material layer 14 to accumulate a charge as high as possible.
Further, the AC plasma display device is increasingly demanded to satisfy a higher density of pixels, a higher fineness and drivability at a lower voltage. For attaining a higher density of pixels and drivability at a lower voltage, it is required to decrease the distance (discharge gap) between a pair of the sustain electrodes 12A and 12B. If the discharge gap is decreased, it is inevitably required to decrease the thickness of the dielectric material layer 14. That is, when the dielectric material layer 14 has a large thickness relative to the discharge gap, most electric lines of flux pass through the dielectric material layer 14, and as a result, glow discharge does not easily take place in the space above the discharge gap.
Meanwhile, if the thickness of the dielectric material layer 14 is decreased, naturally, the voltage resistance decreases. Further, the thickness of the bus electrodes 13A and 13B is greater than the thickness of the sustain electrodes 12A and 12B, and the distance from the top surface of the bus electrodes 13A and 13B to the top surface of the second electrodes 22 is smaller than the distance from the top surface of the sustain electrodes 12A and 12B to the second electrodes 22. Therefore, if the thickness of the dielectric material layer 14 is decreased, therefore, abnormal discharge is liable to take place between the top surface edge portion of the bus electrode 13A or 13B and the second electrode 22, and in a worst case, the bus electrodes 13A or 13B is damaged.
It is therefore a first object of the present invention to provide an alternating current driven type plasma display device structured to increase a charge accumulation amount for improving the brightness, and a method for the production thereof.
It is a second object of the present invention to provide an alternating current driven type plasma display device having a structure in which the abnormal discharge does not easily take place between the bus electrode and the second electrodes as an address electrode even when the discharge gap between a pair of the sustain electrodes and the thickness of the dielectric material layer are decreased for satisfying demands for a higher density of pixels and drivability at a lower voltage, and a method for the production thereof.
The alternating current driven type plasma display device (to be abbreviated as xe2x80x9cplasma display devicexe2x80x9d in some cases, hereinafter) according to a first aspect of the present invention for achieving the above first object is an alternating current driven type plasma display device comprising a first panel and a second panel, said first panel having sustain electrodes formed on a first substrate and a dielectric material layer formed on the first substrate and the sustain electrodes, wherein the first panel and the second panel are bonded to each other in their circumferential portions,
characterized in that the dielectric material layer has a thickness of 1.5xc3x9710xe2x88x925 m or less, preferably 1.0xc3x9710xe2x88x925 m or less.
In the plasma display device according to the first aspect of the present invention, desirably, the lower limit of the dielectric material layer is, for example, 5xc3x9710xe2x88x927 m, and preferably 1xc3x9710xe2x88x926 m. The dielectric material layer may have a single-layered structure or may have a multi-layered structure.
In the plasma display device according to the first aspect of the present invention, since the dielectric material layer has a sufficiently small thickness as compared with a dielectric material layer (generally, approximately 2.5xc3x9710xe2x88x925 m thick) in a conventional AC plasma display device, the capacitance of the dielectric material layer can be increased. As a result, the driving voltage can be decreased, and the charge accumulation amount can be increased, so that the plasma display device can be improved in brightness and that the driving power can be decreased.
The plasma display device according to a second aspect of the present invention for achieving the above first object is an alternating current driven type plasma display device comprising a first panel and a second panel, said first panel having sustain electrodes formed on a first substrate and a dielectric material layer formed on the first substrate and the sustain electrodes, wherein the first panel and the second panel are bonded to each other in their circumferential portions,
characterized in that the dielectric material layer is constituted, at least, of an aluminum oxide layer.
The dielectric material layer of the plasma display device according to the second aspect of the present invention may have a two-layered structure comprising a first dielectric material film constituted of an aluminum oxide layer and a second dielectric material film formed on the first dielectric material film or may have a single-layered structure constituted of an aluminum oxide layer. The material constituting the second dielectric material film includes magnesium oxide (MgO), magnesium fluoride (MgF2) and calcium fluoride (CaF2). Of these, magnesium oxide is a suitable material having properties such as a high emission ratio of secondary electrons, a low sputtering ratio, a high transmissivity to light at a wavelength of light emitted from the fluorescence layers and a low discharge initiating voltage. The second dielectric material film may have a stacked structure composed, at least, of two materials selected from the group consisting of these materials. Second dielectric material films in various alternating current driven type plasma display devices of the present invention to be explained hereinafter can be also composed of the above materials.
The plasma display device according to a third aspect of the present invention for achieving the above first object of the present invention is an alternating current driven type plasma display device comprising a first panel and a second panel, said first panel having sustain electrodes formed on a first substrate and a dielectric material layer formed on the first substrate and the sustain electrodes, wherein the first panel and the second panel are bonded to each other in their circumferential portions, characterized in that the dielectric material layer has a stacked structure constituted, at least, of an aluminum oxide layer and a silicon oxide layer.
In the plasma display device according to the third aspect of the present invention, the stacked structure may be constituted of an aluminum oxide layer and a silicon oxide layer stacked in this order from a bottom, may be constituted of a silicon oxide layer and an aluminum oxide layer stacked in this order from a bottom, or may be constituted of plurality of aluminum oxide layers and silicon oxide layers stacked alternately. In this case, the number of stacked layers may be an even number or may be an odd number. Further, the dielectric material layer may have a multi-layered structure comprising a first dielectric material film constituted of an aluminum oxide layer and a silicon oxide layer and a second dielectric material film formed on the first dielectric material film. When the dielectric material layer has a stacked structure constituted of an aluminum oxide layer and a silicon oxide layer, a stress in the dielectric material layer can be decreased, and cracking of the dielectric material layer can be prevented.
The plasma display device according to a fourth aspect of the present invention for achieving the first object of the present invention is an alternating current driven type plasma display device comprising a first panel and a second panel, said first panel having sustain electrodes formed on a first substrate and a dielectric material layer formed on the first substrate and the sustain electrodes, wherein the first panel and the second panel are bonded to each other in their circumferential portions,
characterized in that the dielectric material layer is constituted, at least, of a silicon oxide layer.
In the plasma display device according to the fourth aspect of the present invention, the dielectric material layer may also have a two-layered structure comprising a first dielectric material film constituted of a silicon oxide layer and a second dielectric material film formed on the first dielectric material film.
The plasma display device according to a fifth aspect of the present invention for achieving the first object of the present invention is an alternating current driven type plasma display device comprising a first panel and a second panel, said first panel having sustain electrodes formed on a first substrate and a dielectric material layer formed on the first substrate and the sustain electrodes, wherein the first panel and the second panel are bonded to each other in their circumferential portions,
characterized in that the dielectric material layer is constituted, at least, of a diamond-like carbon layer, a boron nitride layer or a chromium (III) oxide layer.
In the plasma display device according to the fifth aspect of the present invention, the dielectric material layer may also have a two-layered structure comprising a first dielectric material film constituted of a diamond-like carbon layer, a boron nitride layer or a chromium (III) oxide layer and a second dielectric material film formed on the first dielectric material film.
The plasma display device according to a sixth aspect of the present invention for achieving the first object of the present invention is an alternating current driven type plasma display device comprising a first panel and a second panel, said first panel having sustain electrodes formed on a first substrate and a dielectric material layer formed on the first substrate and the sustain electrodes, wherein the first panel and the second panel are bonded to each other in their circumferential portions,
characterized in that the dielectric material layer has a stacked structure constituted, at least, a layer composed of diamond-like carbon, boron nitride or chromium (III) oxide and a layer composed of silicon oxide or aluminum oxide.
In the plasma display device according to the sixth aspect of the present invention, the structure of the dielectric material layer includes a two-layered structure of layer xe2x80x9cAxe2x80x9d and layer xe2x80x9cBxe2x80x9d from a bottom, a three-layered structure of layer xe2x80x9cAxe2x80x9d, layer xe2x80x9cBxe2x80x9d and layer xe2x80x9cAxe2x80x9d from a bottom and a multi-layered structure of layer xe2x80x9cAxe2x80x9d, layer xe2x80x9cBxe2x80x9d, layer xe2x80x9cAxe2x80x9d, layer xe2x80x9cBxe2x80x9d . . . from a bottom. When the above layer xe2x80x9cAxe2x80x9d is a diamond-like carbon layer, a boron nitride layer or a chromium (III) oxide layer, the layer xe2x80x9cBxe2x80x9d is a silicon oxide or aluminum oxide layer or is a layer having a stacked structure of a silicon oxide layer and an aluminum oxide layer. When two or more layers xe2x80x9cAxe2x80x9d are employed, the layers xe2x80x9cAxe2x80x9d may be composed of one material or different materials, and when two or more layers xe2x80x9cBxe2x80x9d are employed, the layers xe2x80x9cBxe2x80x9d may be composed of one material or different materials. When the layer xe2x80x9cAxe2x80x9d is a silicon oxide or aluminum oxide layer or is a layer having a stacked structure of a silicon oxide layer and an aluminum oxide layer, the layer xe2x80x9cBxe2x80x9d is a diamond-like carbon layer, a boron nitride layer or a chromium (III) oxide layer. In this case, when two or more layers xe2x80x9cAxe2x80x9d are employed, the layers xe2x80x9cAxe2x80x9d may be composed of one material or different materials, and when two or more layers xe2x80x9cBxe2x80x9d are employed, the layers xe2x80x9cBxe2x80x9d may be composed of one material or different materials. When the above silicon oxide or aluminum oxide layer or the above layer having a stacked structure of a silicon oxide layer and an aluminum oxide layer is used as an element for constituting the dielectric material layer, the stress in the dielectric material layer can be decreased, and the cracking of the dielectric material layer can be prevented.
In the plasma display device according to the sixth aspect of the present invention, the dielectric material layer may also have a multi-layered structure comprising a first dielectric material film constituted of the above stacked structure and a second dielectric material film formed on the first dielectric material film.
The plasma display device according to a seventh aspect of the present invention for achieving the first object of the present invention is an alternating current driven type plasma display device comprising a first panel and a second panel, said first panel having sustain electrodes formed on a first substrate and a dielectric material layer formed on the first substrate and the sustain electrodes, wherein the first panel and the second panel are bonded to each other in their circumferential portions,
characterized in that the dielectric material layer is constituted, at least, of two layers selected from the group consisting of a diamond-like carbon layer, a boron nitride layer and a chromium (III) oxide layer.
In the plasma display device according to the seventh aspect of the present invention, the structure of the dielectric material layer includes a two-layered structure of layer xe2x80x9cAxe2x80x9d and layer xe2x80x9cBxe2x80x9d from a bottom, a three-layered structure of layer xe2x80x9cAxe2x80x9d, layer xe2x80x9cBxe2x80x9d and layer xe2x80x9cCxe2x80x9d from a bottom and a multi-layered structure of layer xe2x80x9cAxe2x80x9d, layer xe2x80x9cBxe2x80x9d, layer xe2x80x9cCxe2x80x9d, layer xe2x80x9cDxe2x80x9d . . . from a bottom. The above diamond-like carbon layer, the above boron nitride layer and the above chromium (III) oxide layer will be referred to as xe2x80x9cmaterial layerxe2x80x9d for the convenience. Materials constituting neighboring material layers (for example, layer xe2x80x9cAxe2x80x9d and layer xe2x80x9cBxe2x80x9d) are different from each other. Materials constituting non-neighboring material layers (for example, layer xe2x80x9cAxe2x80x9d and layer xe2x80x9cCxe2x80x9d) may be different from each other or may be the same as each other.
In the plasma display device according to the seventh aspect of the present invention, the dielectric material layer may further have a silicon oxide layer or an aluminum oxide layer or may further have a stacked structure of a silicon oxide layer and an aluminum oxide layer. In the above embodiment, when the dielectric material layer further has, for example, a silicon oxide layer, the structure of the dielectric material layer includes a three-layered structure of a silicon oxide layer, layer xe2x80x9cAxe2x80x9d and layer xe2x80x9cBxe2x80x9d from a bottom, a three layered structure of layer xe2x80x9cAxe2x80x9d, a silicon oxide layer and layer xe2x80x9cBxe2x80x9d and a three-layered structure of layer xe2x80x9cAxe2x80x9d, layer xe2x80x9cBxe2x80x9d and a silicon oxide layer. In the three-layered structure of layer xe2x80x9cAxe2x80x9d, layer xe2x80x9cBxe2x80x9d and layer xe2x80x9cCxe2x80x9d or the multi-layered structure of layer xe2x80x9cAxe2x80x9d, layer xe2x80x9cBxe2x80x9d, layer xe2x80x9cCxe2x80x9d, layer xe2x80x9cDxe2x80x9d . . . , at least one silicon oxide layer can be interposed between any two material layers or can be placed as a topmost material layer or a bottommost material layer. When a silicon oxide layer, an aluminum oxide layer or a stacked structure of a silicon oxide layer and an aluminum oxide layer is used as an element for constituting the dielectric material layer as described above, the stress in the dielectric material layer can be decreased, and the cracking of the dielectric material layer can be prevented.
In the plasma display device according to the seventh aspect of the present invention, the dielectric material layer may have a multi-layered structure comprising a first dielectric material film constituted of the above stacked structure and a second dielectric material film formed on the first dielectric material film.
In the plasma display device according to any one of the second to seventh aspects of the present invention, desirably, the thickness of the dielectric material layer is 1.5xc3x9710xe2x88x925 m or less, preferably 1.0xc3x9710xe2x88x925 m or less. Desirably, the lower limit of the thickness of the dielectric material layer is, for example, 5xc3x9710xe2x88x927 m, preferably 1xc3x9710xe2x88x926 m. When the dielectric material layer comprises the first dielectric material film and the second dielectric material film, the thickness of the dielectric material layer is a total thickness of the first dielectric material film and the second dielectric material film. When the dielectric material layer comprises the first dielectric material film and the second dielectric material film, the thickness of the second dielectric material film is preferably 1xc3x9710xe2x88x926 m to 1xc3x9710xe2x88x925 m. When the thickness of the dielectric material layer is defined as described above, the capacitance of the dielectric material layer can be increased. As a result, the driving voltage can be decreased, and the charge accumulation amount can be increased, so that the brightness of the plasma display device can be improved and the driving power thereof can be decreased.
In the plasma display device according to any one of the first to seventh aspects of the present invention, the sustain electrodes formed in the first panel can be constituted to work as a pair. The distance between the sustain electrodes constituting each pair is essentially any distance so long as the glow discharge required takes place at a predetermined discharge voltage. Desirably, the distance between a pair of the sustain electrodes is less than 5xc3x9710xe2x88x925 m, preferably less than 5.0xc3x9710xe2x88x925 m, and more preferably 2xc3x9710xe2x88x925 m or less. When the distance between a pair of the sustain electrodes is approximately 1xc3x9710xe2x88x924 m, and when the thickness of the dielectric material layer is too large, there are some cases where discharge breakdown takes place in the dielectric material layer and a charge is not easily accumulated in the dielectric material layer. In the plasma display device according to the first aspect of the present invention, since the dielectric material layer has a small thickness as compared with a conventional case, and in the plasma display device according to any one of the second to seventh aspects of the present invention, when the dielectric material layer has a small thickness as compared with a conventional case, that is, the thickness of the dielectric material layer is defined to be 1.5xc3x9710xe2x88x925 m or less, desirably, 1.0xc3x9710xe2x88x925 m or less, the above phenomenon can be reliably inhibited.
In the plasma display device according to any one of the second to seventh aspects of the present invention, the dielectric material layer is composed of a material having a relatively large specific dielectric constant (for example, an aluminum oxide layer formed by a sputtering method has a specific dielectric constant of 9 to 10), whereby the capacitance of the dielectric material layer can be increased. As a result, the charge accumulation amount can be increased, so that the plasma display device can be improved in brightness and the driving power thereof can be decreased.
In the plasma display device according to the present invention including an alternating current driven type plasma display device according to an eighth aspect of the present invention to be described later, since the dielectric material layer is formed, the direct contact of ions or electrons to the sustain electrodes can be prevented. As a result, wearing of the sustain electrodes can be prevented. The dielectric material layer not only works to accumulate a wall charge but also works as a resistance material to limit an excess discharge current and works as a memory to sustain a discharge state.
In the plasma display device according to any one of the first to seventh aspect of the present invention, there may be employed a constitution in which one of a pair of the sustain electrodes is formed in the first panel and the other is formed in the second panel. The thus-constituted plasma display device will be called xe2x80x9cbi-electrode typexe2x80x9d for convenience. In this case, the projection image of one sustain electrode extends in a first direction, the projection image of the other extends in a second direction different from the first direction, and a pair of the sustain electrodes are arranged such that one sustain electrode faces the other. Alternatively, there may be employed a constitution in which a pair of the sustain electrodes are formed in the first panel and a so-called address electrode (second electrode) is formed in the second panel. The thus-constituted plasma display device will be referred to as xe2x80x9ctri-electrode typexe2x80x9d for convenience. In this case, there may be employed a constitution in which the projection images of a pair of the sustain electrodes extend in a first direction in parallel with each other, the projection image of the address electrode (second electrode) extends in a second direction and a pair of the sustain electrodes and the address electrode (second electrode) are arranged such that a pair of the sustain electrodes face the address electrode, although the constitution shall not be limited thereto. In these cases, in view of the structural simplification of the plasma display device, preferably, the first direction and the second direction cross each other at right angles.
In the plasma display device according to any one of the first to seventh aspects of the present invention, the form of a gap between facing edge portions of a pair of the sustain electrodes formed in the first panel may be linear. Alternatively, the form of the above gap may have a pattern bent or curved in the width direction of the sustain electrodes. In this case, the area of portions of the sustain electrodes which portions contribute to discharging can be increased.
The plasma display device according to an eighth aspect of the present invention for achieving the above second object is an alternating current driven type plasma display device comprising;
(1) a first panel having a first substrate; a first electrode group consisting of a plurality of first electrodes formed on the first substrate; and a dielectric material layer which covers the first electrodes and is constituted of a first dielectric material layer and a second dielectric material layer, and
(2) a second panel having a second substrate; a second electrode group consisting of a plurality of second electrodes extending while making a predetermined angle with the extending direction of the first electrodes, said second electrodes being formed on the second substrate; separation walls each of which is formed between one second electrode and another neighboring second electrode; and fluorescence layers formed on or above the second electrodes,
wherein each first electrode comprises;
(A) a first bus electrode,
(B) a first sustain electrode being in contact with the first bus electrode,
(C) a second bus electrode extending in parallel with the first bus electrode, and
(D) a second sustain electrode being in contact with the second bus electrode and facing the first sustain electrode,
and wherein discharge takes place between the first sustain electrode and the second sustain electrode,
said plasma display device characterized in that a first portion of the dielectric material layer which portion covers the first bus electrode and the second bus electrode comprises the first dielectric material layer and the second dielectric material layer, and a second portion of the dielectric material layer which covers the first sustain electrode and the second sustain electrode comprises the first dielectric material layer.
In the plasma display device according to the eighth aspect of the present invention or in a production method according to a third aspect of the present invention to be described later, since the first portion of the dielectric material layer which portion covers the first bus electrode and the second bus electrode comprises the first dielectric material layer and the second dielectric material layer, abnormal discharge, for example, between a top surface of the bus electrode and the second electrode can be reliably prevented. The dielectric material layer as a whole works to accumulate a wall charge, works as a resistance material to limit an excess discharge current and works as a memory to sustain a discharge state.
In the plasma display device according to the eighth aspect of the present invention, there may be employed a constitution in which the element constituting a first bus electrode and the element constituting a first electrode neighboring on said first bus electrode are independent of each other, or there may be employed a constitution in which a first bus electrode constituting a first electrode and a second bus electrode constituting a first electrode neighboring on said first electrode are in common (i.e., said first bus electrode and said second electrode are constituted of one conductive material layer, for example, in the form of a stripe). A plasma display device having the former constitution will be referred to as a plasma display device according to the first constitution, and a plasma display device having the latter constitution will be referred to as a plasma display device according to the second constitution. In the plasma display device according to the second constitution of the present invention, the first portion of the dielectric material layer which portion covers the first bus electrode constituting the first electrode and the first portion of the dielectric material layer which portion covers the second bus electrode constituting the first electrode neighboring on said first electrode are in common. xe2x80x9cThe plasma display device according to the eighth aspect of the present inventionxe2x80x9d to be described hereinafter includes the plasma display devices according to the first and second constitutions of the present invention. In the plasma display device according to the second constitution of the present invention, the first bus electrode and the second bus electrode which are in common will be sometimes referred to as xe2x80x9ccommon bus electrodexe2x80x9d, and when the first bus electrode and the second bus electrode are explained hereinafter, these can be read as a common bus electrodes.
In the plasma display device according to the eighth aspect of the present invention, the first portion of the dielectric material layer may be formed by stacking the first dielectric material layer and the second dielectric material layer in this order from the first substrate, or by stacking the second dielectric material layer and the first dielectric material layer in this order from the first substrate.
The plasma display device according to the eighth aspect of the present invention is a so-called tri-electrode type surface-discharge type plasma display device. The plasma display device according to the eighth aspect of the present invention is structured as follows. The first panel and the second panel are arranged such that the dielectric material layer and the fluorescence layers face each other, the extending direction of projection image of the first electrodes (more specifically, the bus electrodes) and the extending direction of projection image of the second electrodes makes a predetermined angle (for example, 90xc2x0), a space surrounded by the dielectric material layer, the fluorescence layer and a pair of the separation walls is charged with a rare gas, and the fluorescence layer emits light when irradiated with vacuum ultraviolet ray generated on the basis of AC glow discharge in the rare gas between a pair of the facing sustain electrodes. A region where one first electrode (a combination of a pair of the first sustain electrode and the second sustain electrode and a pair of the first bus electrode and the second bus electrode) and a pair of the separation walls overlap corresponds to one discharge cell (one sub-pixel). The extending direction of the first electrodes (more specifically, the bus electrodes) will be referred to as xe2x80x9cfirst directionxe2x80x9d, and the extending direction of the second electrodes will be referred to as xe2x80x9csecond directionxe2x80x9d, hereinafter.
The plasma display device production method according to a first aspect of the present invention for achieving the above first object is a method for producing an alternating current driven type plasma display device comprising a first panel and a second panel, said first panel having sustain electrodes formed on a first substrate and a dielectric material layer formed on the first substrate and the sustain electrodes, wherein the first panel and the second panel are bonded to each other in their circumferential portions,
said method including a step of forming the dielectric material layer having a thickness of 1.5xc3x9710xe2x88x925 m or less, preferably 1.0xc3x9710xe2x88x925 m or less on the first substrate and the sustain electrodes by a physical vapor deposition method (PVD method) such as a sputtering method, a vacuum deposition method or an ion plating method or a chemical vapor deposition method (CVD method). The above PVD method or CVD method makes it possible to form a dielectric material layer having a small and uniform layer thickness.
Although differing depending upon materials for the dielectric material layer, specifically, the above PVD method includes;
(a) various vacuum deposition methods such as an electron beam heating method, a resistance heating method and a flash deposition method,
(b) a plasma deposition method,
(c) various sputtering methods such as a diode sputtering method, a DC sputtering method, a DC magnetron sputtering method, a high-frequency sputtering method, a magnetron sputtering method, an ion-beam sputtering method and a bias sputtering method, and
(d) various ion-plating methods such as a DC (direct current) method, an RF method, a multi-cathode method, an activation reaction method, an electric field deposition method, a high-frequency ion-plating method and a reactive ion plating method.
Although differing depending upon a material for the dielectric material layer, the CVD method includes an atmospheric pressure CVD method (APCVD method), a reduced pressure CVD method (LPCVD method), a low-temperature CVD method, a high-temperature CVD method, a plasma CVD method (PCVD method, PECVD method), an ECR plasma CVD method, a photo CVD method and an MOCVD method.
The plasma display device production method according to a second aspect of the present invention for achieving the above first object is a method for producing an alternating current driven type plasma display device comprising a first panel and a second panel, said first panel having sustain electrodes formed on a first substrate and a dielectric material layer formed on the first substrate and the sustain electrodes, wherein the first panel and the second panel are bonded to each other in their circumferential portions,
said method including a step of forming the dielectric material layer having a thickness of 1.5xc3x9710xe2x88x925 m or less, preferably 1.0xc3x9710xe2x88x925 m or less on the first substrate and the sustain electrodes from a solution containing a dielectric material.
In the plasma display device production method according to the second aspect of the present invention, the step of forming the dielectric material layer may comprise a step of applying the solution containing a dielectric material onto the first substrate and the sustain electrodes by a spin-coating method. Alternatively, in the above method, the step of forming the dielectric material layer may comprise a step of screen-printing the solution (including a paste) containing a dielectric material on the first substrate and the sustain electrodes. The solution containing a dielectric material includes a water glass and a suspension of glass powders. Although differing depending upon a material for the dielectric material, the application of the solution containing a dielectric material is followed by drying, and calcining or sintering, whereby the dielectric material layer can be obtained.
The above water glass can be selected from No. 1 to No. 4 water glasses defined in Japanese Industrial Standard (JIS) K1408 or materials equivalent thereto. The No. 1 to No. 4 refer to four grades based on differences (approximately 2 to 4 mol) in molar amount of silicon oxide (SiO2) per mole of sodium oxide (Na2O) as a component of the water glasses, and the No. 1 to No. 4 water glasses greatly differ from one another in viscosity. When water glass is used, therefore, a water glass of an optimum grade having a viscosity suitable for screen printing is selected, or water glass equivalent to such a grade is prepared. The solvent for the water glass includes water and organic solvents such as alcohols. For attaining a viscosity suitable for the screen printing, preferably, a dispersing agent or a surfactant is added.
The plasma display device production method according to a third aspect of the present invention for achieving the above second object is a method for producing the plasma display device according to the eighth aspect of the present invention including the plasma display device according to the first or second constitution of the present invention. That is, the above method is for producing an alternating current driven type plasma display device comprising;
(1) a first panel having a first substrate; a first electrode group consisting of a plurality of first electrodes formed on the first substrate; and a dielectric material layer which covers the first electrodes and comprises a first dielectric material layer and a second dielectric material layer, and
(2) a second panel having a second substrate; a second electrode group consisting of a plurality of second electrodes extending while making a predetermined angle with the extending direction of the first electrodes, said second electrodes being formed on the second substrate; separation walls each of which is formed between one second electrode and another neighboring second electrode; and fluorescence layers formed on or above the second electrodes,
wherein each first electrode comprises;
(A) a first bus electrode,
(B) first sustain electrode being in contact with the first bus electrode,
(C) a second bus electrode extending in parallel with the first bus electrode, and
(D) a second sustain electrode being in contact with the second bus electrode and facing the first sustain electrode,
and wherein discharge takes place between the first sustain electrode and the second sustain electrode,
said method including the steps of;
(a) forming the first electrode group on the first substrate, and
(b) either covering the first electrodes with the first dielectric material layer, followed by forming the second dielectric material layer on portions of the first dielectric material layer above the first bus electrode and the second bus electrode, or covering the first bus electrode and the second bus electrode with the second dielectric material layer, following by covering the first electrode with the first dielectric material layer.
In the step (b) in the alternating current driven type plasma display device production method according to the third aspect of the present invention, the first electrode is covered with the first dielectric material layer and then the second dielectric material layer is formed on the portions of the first dielectric material layer above the first bus electrode and the second bus electrode. In this case, the first portion of the dielectric material layer has a constitution in which the first dielectric material layer and the second dielectric material layer are stacked in this order from the first substrate side. The above xe2x80x9ccovering of the first electrode with the first dielectric material layerxe2x80x9d means the formation of the first dielectric material layer on (upper surfaces and side surfaces of) the first sustain electrode constituting the first electrode, the first bus electrode, the second sustain electrode and the second bus electrode. The formation of the second dielectric material layer on the portions of the first dielectric material layer above the first bus electrode and the second bus electrode means the formation of the second dielectric material layer on top surfaces and side surfaces of the first bus electrode and the second bus electrode through the first dielectric material layer.
Otherwise, in the step (b) in the plasma display device production method according to the third aspect of the present invention, the first bus electrode and the second bus electrode are covered with the second dielectric material layer and then the first electrode is covered with the first dielectric material layer. In this case, the first portion of the dielectric material layer has a constitution in which the second dielectric material layer and the first dielectric material layer are stacked in this order from the first substrate side. The above xe2x80x9ccovering of the first electrode with the first dielectric material layerxe2x80x9d means the formation of the first dielectric material layer on (upper surfaces and side surfaces of) the first sustain electrode, the first bus electrode, the second sustain electrode and the second bus electrode constituting the first electrode. Further, the above xe2x80x9cforming the second dielectric material layer on portions of the first dielectric material layer above the first bus electrode and the second bus electrodexe2x80x9d means the formation of the second dielectric material layer on the top surfaces and the side surfaces of the first bus electrode and the second bus electrode through the first dielectric material layer.
In the plasma display device according to the eighth aspect of the present invention or the production method according to the third aspect of the present invention, preferably, the second portion of the dielectric material layer which portion covers the first and second sustain electrodes has a thickness of 1xc3x9710xe2x88x925 m or less for complying with demands of higher density of pixels and lower driving voltage. The thickness of the second portion of the dielectric material layer which portion covers the first and second sustain electrodes refers to a thickness in the top surfaces of the first and second sustain electrodes. The lower limit of the thickness of the second portion of the dielectric material layer can be such a thickness that no abnormal discharge takes place between the first sustain electrode and the second sustain electrode, and desirably, the lower limit is, for example, 1xc3x9710xe2x88x926 m, preferably 2xc3x9710xe2x88x926 m.
In the plasma display device according to the eighth aspect of the present invention or the production method according to the third aspect of the present invention, desirably, the second dielectric material layer of the top surfaces of the first bus electrode and the second bus electrode has a thickness (t2) of 5xc3x9710xe2x88x926 m to 3xc3x9710xe2x88x925 m, preferably 1xc3x9710xe2x88x925 m to 2xc3x9710xe2x88x925 m, from the viewpoint of preventing abnormal discharge between the bus electrode and the second electrode.
In the plasma display device according to the first constitution of the present invention or the production method thereof, the first dielectric material layer and the second dielectric material layer may be formed on the first substrate between the first bus electrode constituting the first electrode and the second bus electrode constituting the first electrode neighboring on said first electrode. This constitution can effectively prevent abnormal discharge between the first bus electrode constituting the first electrode and the second bus electrode constituting the first electrode neighboring on said first electrode.
In the plasma display device according to the eighth aspect of the present invention or in the step (b) of the production method according to the third aspect of the present invention, the second dielectric material layer may be further formed on or above a region of the first panel which region corresponds to the separation wall formed in the second panel. This constitution can reliably prevent a so-called optical crosstalk phenomenon in which glow discharge has an influence on neighboring discharge cells.
In the plasma display device according to the eighth aspect of the present invention or the production method according to the third aspect of the present invention, preferably, the material constituting the first dielectric material layer differs from the material constituting the second dielectric material layer. There may be employed a constitution in which the first dielectric material layer is composed of silicon oxide (SiO2) and the second dielectric material layer is composed of a calcined or sintered product of a glass plate (more specifically, a low-melting glass paste). In this constitution, preferably, the first dielectric material layer is formed by a chemical vapor deposition method (CVD method) or a physical vapor deposition method (PVD method) such as a sputtering method and a vacuum deposition method, and the second dielectric material layer is formed by a printing method (screen printing method). If the first dielectric material layer is formed particularly by a CVD method, there can be reliably formed the first dielectric material layer which is conformal and is excellent in step coverage and layer thickness uniformity.
In the plasma display device according to the eighth aspect of the present invention or the production method according to the third aspect of the present invention, the second dielectric material layer may be colored. In this case, the second dielectric material layer can exhibit a function of a black matrix, and a contrast among pixels in the second direction can be improved.
In the plasma display device according to the eighth aspect of the present invention or the production method according to the third aspect of the present invention, the first bus electrode and the second bus electrode are common in discharge cells neighboring on each other in the first direction. The first sustain electrode and the second sustain electrode may be common in discharge cells neighboring on each other in the first direction (that is, the first sustain electrode may extend in parallel with the first bus electrode and the second sustain electrode may extend in parallel with the second bus electrode), or may be formed between a pair of separation walls (that is, they may be formed for each discharge cell). A portion of the first sustain electrode which portion faces the second sustain electrode and a portion of the second sustain electrode which portion faces the first sustain electrode may be linear or may be in a zigzag form (for example, a combination of xe2x80x9cdoglegxe2x80x9d forms, a combination of xe2x80x9cSxe2x80x9d letters, a combination of arc forms or a combination of any curved forms). When the first sustain electrode and the second sustain electrode are formed between a pair of the separation walls, the plan form of the first sustain electrode and the second sustain electrode may have a constitution in which, as shown in FIG. 14, the first sustain electrode extends from the first bus electrode toward the second bus electrode in parallel with the second direction, the second sustain electrode extends from the second bus electrode toward the first bus electrode in parallel with the second direction, and discharge such as glow discharge takes place between a top end portion of the first sustain electrode and a top end portion of the second sustain electrode. Alternatively, there may be employed a constitution in which, as shown in FIG. 15 or 16, the first sustain electrode extends from the first bus electrode toward the second bus electrode and extends short of the second bus electrode in parallel with the second direction, the second sustain electrode extends from the second bus electrode toward the first bus electrode and extends short of the first bus electrode in parallel with the second direction so as to face the first sustain electrode (or along the first sustain electrode), and discharge such as glow discharge takes place between a portion (side surface) of the first sustain electrode which portion faces the second sustain electrode and a portion (side surface) of the second sustain electrode which portion faces the first sustain electrode.
In the plasma display device according to the eighth aspect of the present invention or the production method according to the third aspect of the present invention, the distance (L1) between the first sustain electrode and the second sustain electrode may essentially have any value. However, desirably, it is 1xc3x9710xe2x88x924 m or less, preferably less than 5xc3x9710xe2x88x925 m, more preferably 4xc3x9710xe2x88x925 m or less, still more preferably 2.5xc3x9710xe2x88x925 m or less. The lower limit of the distance (L1) between the first sustain electrode and the second sustain electrode can be determined to be any value while taking account of the thickness of the dielectric material layer, etc., such that no dielectric breakdown takes place between the first sustain electrode and the second sustain electrode.
The plasma display device according to any one of the first to eighth aspects of the present invention will be explained below by referring, for example, to a tri-electrode type plasma display device. With regard to a bi-electrode type plasma display device, the second electrode in the following explanation can be read as xe2x80x9cthe other sustain electrodexe2x80x9d.
In the plasma display device according to any one of the first to seventh aspects of the present invention or the production method according to the first and second aspects of the present invention, there may be also employed a constitution in which, in addition to the sustain electrode, a bus electrode composed of a material having a lower electric resistivity than the sustain electrode is formed in contact with the sustain electrode for decreasing the impedance of the sustain electrode as a whole. In the plasma display device according to any one of the first to eighth aspects of the present invention or the production method according to any one of the first to third aspects of the present invention, it is preferred to employ a constitution in which the electrically conductive material for the sustain electrode and the electrically conductive material for the bus electrode differ from each other. Typically, the bus electrode can be composed, for example, of Ag, Au, Al, Ni, Cu, Mo, Cr or a Cr/Cu/Cr stacked film. The bus electrode composed of the above metal material in a reflection-type plasma display device decreases the transmitted-light quantity of visible light which is emitted from the fluorescence layer and passes through the first substrate, so that the brightness of a display screen is decreased. It is therefore preferred to form the bus electrode so as to be as narrow as possible so long as an electric resistance value necessary for the bus electrode can be obtained. The bus electrode can be formed, for example, by a deposition method, a sputtering method, a printing method (screen printing method), a sand blasting method, a plating method or a lift-off method as required depending upon an electrically conductive material used. That is, the bus electrode having a predetermined pattern from the beginning can be formed with a proper mask or a screen, or the bus electrode can be formed by forming an electrically conductive material layer on the entire surface and then patterning the electrically conductive material layer.
In the plasma display device according to any one of the first to eighth aspects of the present invention or the production method according to any one of the first to third aspects of the present invention, the electrically conductive material for the sustain electrode differs depending upon whether the plasma display device is a transmission type or a reflection type. In the transmission type plasma display device, light emission from the fluorescence layer is observed through the second panel, so that it is not any problem whether the electrically conductive material constituting the sustain electrode is transparent or non-transparent. However, since the second electrode (address electrode) is formed on the second substrate, the second electrode is desirably transparent. In the reflection type plasma display device, light emission from the fluorescence layers is observed through the first substrate, so that it is not a problem whether the electrically conductive material constituting the second electrode (address electrode) is transparent or non-transparent. However, the electrically conductive material constituting the sustain electrodes is desirably transparent. The term xe2x80x9ctransparent or non-transparentxe2x80x9d is based on the transmissivity of the electrically conductive material to light at a wavelength of emitted light (in visible light region) inherent to fluorescence materials. That is, when an electrically conductive material constituting the sustain electrode is transparent to light emitted from the fluorescence layers, it can be said that the electrically conductive material is transparent. The non-transparent electrically conductive material includes Ni, Al, Au, Ag, Pd/Ag, Cr, Ta, Cu, Ba, LaB6, Ca0.2La0.8CrO3, etc., and these materials may be used alone or in combination. The transparent electrically conductive material includes ITO (indium-tin oxide) and SnO2. The sustain electrode can be formed, for example, by a deposition method, a sputtering method, a printing method (screen printing method), a sand blasting method, a plating method or a lift-off method as required depending upon an electrically conductive material used. That is, the sustain electrode having a predetermined pattern from the beginning can be formed with a proper mask or a screen, or the sustain electrode can be formed by forming an electrically conductive material layer on the entire surface and then patterning the electrically conductive material layer.
In the reflection type plasma display device, the material for the dielectric material layer is required to be transparent since light emitted from the fluorescence layer is observed through the first substrate.
In the plasma display device according to the eighth aspect of the present invention or the production method according to the third aspect of the present invention, preferably, a protective layer is formed at least on the surface of the second portion of the dielectric material layer which portion covers the first sustain electrode and the second sustain electrode. The protective layer may be formed not only on the second portion but also on the surface of the first portion of the dielectric material layer which portion covers the first bus electrode and the second bus electrode. The protective layer may have a single-layered structure or a stacked-layered structure. In the plasma display device production method according to the third aspect of the present invention, the protective layer may be formed after the step (b), or in the step (b), the protective layer may be formed after the first electrodes are covered with the first dielectric material layer, followed by the formation of the second dielectric material layer on the portion of the first dielectric material layer (more specifically, on the protective layer) above the first bus electrode and the second bus electrode. The material constituting the protective layer having a single-layered structure includes magnesium oxide (MgO), magnesium fluoride (MgF2), calcium fluoride (CaF2) and aluminum oxide (Al2O3). Of these, magnesium oxide is a suitable material having properties such as chemical stability, a low sputtering ratio, a high light transmissivity at a wavelength of light emitted from the fluorescence layers and a low discharge initiating voltage. The protective layer may have a stacked-layered structure composed of at least two materials selected from the group consisting of magnesium oxide, magnesium fluoride and aluminum oxide. When the protective layer is formed, the direct contact of ions or electrons to the first electrode group can be prevented, and as a result, the wearing of the first electrodes can be prevented. The protective layer also works to emit secondary electrons necessary for glow discharge.
In the plasma display device according to the eighth aspect of the present invention or the production method according to the third aspect of the present invention, the second electrode is formed on the second substrate. If the function of the fluorescence layer as a dielectric substance layer is insufficient, a dielectric substance layer may be formed between the second electrode group and the fluorescence layer. The material for the dielectric substance layer can be selected from a low-melting glass or SiO2.
The fluorescence layer is composed of a fluorescence material selected from the group consisting of a fluorescence material which emits light in red, a fluorescence material which emits light in green and a fluorescence material which emits light in blue. The fluorescence layer is formed on or above the second substrate (or the second electrode). Specifically, the fluorescence layer composed of a fluorescence material which emits light, for example, of a red color (red fluorescence layer) is formed on or above the second electrode, the fluorescence layer composed of a fluorescence material which emits light, for example, of a green color (green fluorescence layer) is formed on or above another second electrode, and the fluorescence layer composed of a fluorescence material which emits light, for example, of a blue color (blue fluorescence layer) is formed on or above still another second electrode. These three fluorescence layers for emitting light of three primary colors form one set, and such sets are formed in a predetermined order. A region where one first electrode (a combination of a pair of the first bus electrode and the second bus electrode and a pair of the first sustain electrode and the second sustain electrode) and one set of the fluorescence layers which emit light of three primary colors overlap corresponds to one pixel. The red fluorescence layers, the green fluorescence layers and the blue fluorescence layers may be formed in the form of stripes, or may be formed in the form of dots. When the red fluorescence layer, the green fluorescence layer and the blue fluorescence layer are formed in the form of stripes, one red fluorescence layer is formed on or above one second electrode, one green fluorescence layer is formed on or above one second electrode, and one blue fluorescence layer is formed on or one second electrode. When the red fluorescence layer, the green fluorescence layer and the blue fluorescence layer are formed in the form of dots, the red fluorescence layer, the green fluorescence layer and the blue fluorescence layer are formed on or above one second electrode in a predetermined order. Further, the fluorescence layers may be formed only on regions where the sustain electrodes and the second electrodes overlap.
The fluorescence layer may be formed directly on the second electrode, or it may be formed on the second electrode and on the side walls of the separation walls. Alternatively, the fluorescence layer may be formed on the dielectric substance layer formed on the second electrode or may be formed on the dielectric substance layer formed on the second electrode and on the side walls of the separation walls. Alternatively, the fluorescence layer may be formed only on the side walls of the separation walls. The formation of the fluorescence layer on or above the second electrode includes all of the above various embodiments.
The material for the dielectric substance layer includes a low-melting glass and silicon oxide, and it can be formed by a screen printing method, a sputtering method or a vacuum deposition method. In some cases, a protective layer composed of magnesium oxide (MgO), magnesium fluoride (MgF2) or calcium fluoride (CaF2) may be formed on the fluorescence layer and the separation wall.
As the fluorescence material for constituting the fluorescence layers, fluorescence materials which have high quantum efficiency and cause less saturation to vacuum ultraviolet ray can be selected from known fluorescence materials as required. When the plasma display device is used as a color display, it is preferred to combine those fluorescence materials which have color purities close to three primary colors defined in NTSC, which have an excellent white balance when three primary colors are mixed, which show a small afterglow time period and which can secure that the afterglow time periods of three primary colors are nearly equal. Examples of the fluorescence material which emits light in red when irradiated with vacuum ultraviolet ray include (Y2O3:Eu), (YBO3Eu), (YVO4:Eu), (Y0.96P0.60V0.40O4:Eu0.04), [(Y,Gd)BO3:Eu], (GdBO3:Eu), (ScBO3:Eu) and (3.5MgOxc2x70.5MgF2xc2x7GeO2:Mn). Examples of the fluorescence material which emits light in green when irradiated with vacuum ultraviolet light include (ZnSiO2:Mn), (BaAl12O19:Mn), (BaMg2Al16O27:Mn), (MgGa2O4:Mn), (YBO3:Tb), (LuBO3:Tb) and (Sr4Si3O8Cl4:Eu). Examples of the fluorescence material which emits light in blue when irradiated with vacuum ultraviolet ray include (Y2SiO5:Ce), (CaWO4:Pb), CaWO4, YP0.85V0.15O4, (BaMgAl14O23:Eu), (Sr2P2O7:Eu) and (Sr2P2O7:Sn). The method for forming the fluorescence layers includes a thick film printing method, a method in which fluorescence material particles are sprayed, a method in which an adhesive substance is pre-applied to regions where the fluorescence layers are to be formed and fluorescence particles are allowed to adhere, a method in which a photosensitive fluorescence paste is provided and a fluorescence layer is patterned by exposure and development of the photosensitive fluorescence paste, and a method in which a fluorescence layer is formed on the entire surface and unnecessary portions thereof are removed by a sand blasting method.
The separation walls may have a constitution in which they extend in regions between neighboring second electrodes in parallel with the second electrodes. That is, there may be employed a constitution in which one second electrode extends between a pair of the separation walls. In some cases, the separation walls may have a constitution in which a first separation wall extends in a region between neighboring bus electrodes in parallel with the bus electrodes and a second separation wall extends in a region between neighboring second electrodes in parallel with the second electrodes (that is, in the form of a grille). While the separation walls in the form of a grille (lattice) are conventionally used in a DC driven type plasma display device, they can be applied to the plasma display device of the present invention. The separation walls (ribs) may have a meander structure. When the dielectric substance layer is formed on the second substrate and on the address electrode, the separation walls may be formed on the dielectric substance layer in some cases.
The material for the separation wall can be selected from a known insulating material. For example, a mixture of a widely used low-melting glass with a metal oxide such as alumina can be used. The separation wall can be formed by a screen printing method, a sand blasting method, a dry filming method and a photosensitive method. The above screen printing method refers to a method in which opening portions are made in those portions of a screen which correspond to portions where the separation walls are to be formed, a separation-wall-forming material on the screen is passed through the opening portions with a squeeze to form a separation-wall-forming material layer on the second substrate or the dielectric substance layer (these will be generically referred to as xe2x80x9csecond substrate or the likexe2x80x9d hereinafter), and then the separation-wall-forming material layer is calcined or sintered. The above dry filming method refers to a method in which a photosensitive film is laminated on the second substrate or the like, the photosensitive film on regions where the separation walls are to be formed is removed by exposure and development, opening portions formed by the removal are filled with a separation-wall-forming material and the separation-wall-forming material is calcined or sintered. The photosensitive film is combusted and removed by the calcining or sintering and the separation-wall-forming material filled in the opening portions remains to constitute the separation walls. The above photosensitive method refers to a method in which a photosensitive material layer for forming the separation walls is formed on the second substrate or the like, the photosensitive material layer is patterned by exposure and development and then the patterned photosensitive material layer is calcined or sintered. The above sand blasting method refers to a method in which a separation-wall-forming material layer for forming the separation walls is formed on the second substrate or the like, for example, by screen printing or with a roll coater, a doctor blade or a nozzle-ejecting coater and is dried, then, those portions where the separation walls are to be formed in the separation-wall-forming material layer are covered with a mask layer and exposed portions of the separation-wall-forming material layer are removed by a sand blasting method. The separation walls may be formed in black to form a so-called black matrix. In this case, a high contrast of the display screen can be attained. The method of forming the black separation walls includes a method in which a light-absorbing layer such as a photosensitive silver paste layer or a low-reflection chromium layer is formed on the top portion of each separation wall and a method in which the separation walls are formed from a color resist material colored in black.
The material constituting the first substrate for the first panel and the second substrate for the second panel includes high-distortion-point glass, soda glass (Na2Oxc2x7CaOxc2x7SiO2), borosilicate glass (Na2Oxc2x7B2O3xc2x7SiO2), forsterite (2MgOxc2x7SiO2) and lead glass (Na2Oxc2x7PbOxc2x7SiO2). The material constituting the first substrate and the material constituting the second substrate may be the same as, or different from, each other.
One discharge cell is constituted of a pair of the separation walls formed above the second panel, the sustain electrodes and the second electrode occupying a region surrounded by a pair of the separation walls, and the fluorescence layer (for example, one fluorescence layer of the red fluorescence layer, the green fluorescence layer and the blue fluorescence layer). The discharge gas consisting of a mixed gas is sealed in the above discharge cell, more specifically, the discharge space surrounded by the separation walls, and the fluorescence layer emits light when irradiated with vacuum ultraviolet ray generated by AC glow discharge which takes place in the discharge gas in the discharge space.
In the plasma display device of the present invention, desirably, a rare gas charged in the space surrounded by the dielectric material layer, the fluorescence layer and a pair of the separation walls has a pressure of 1.0xc3x97102 Pa (0.001 atmospheric pressure) to 5xc3x97105 Pa (5 atmospheric pressures), preferably 1xc3x97103 Pa (0.01 atmospheric pressure) to 4xc3x97105 Pa (4 atmospheric pressures). When the distance L1 between a par of the sustain electrodes is less than 5xc3x9710xe2x88x925 m, desirably, the pressure of the rare gas in the space is 1.0xc3x97102 Pa (0.001 atmospheric pressure) to 3.0xc3x97105 Pa (3 atmospheric pressures), preferably 1.0xc3x97103 Pa (0.01 atmospheric pressure) to 2.0xc3x97105 Pa (2 atmospheric pressures), more preferably 1.0xc3x97104 Pa (0.1 atmospheric pressure) to 1.0xc3x97105 Pa (1 atmospheric pressure). When the pressure of the rare gas is adjusted to the above pressure range, the fluorescence layer emits light when irradiated with vacuum ultraviolet ray generated mainly on the basis of cathode glow in the rare gas. With an increase in pressure in the above pressure range, the sputtering ratio of various members constituting the plasma display device decreases, which results in an increase in the lifetime of the plasma display device.
The rare gas to be sealed in the space is required to satisfy the following requirements.
(1) The rare gas is chemically stable and permits setting of a high gas pressure from the viewpoint of attaining a longer lifetime of the plasma display device.
(2) The rare gas permits the high radiation intensity of vacuum ultraviolet ray from the viewpoint of attaining higher brightness of a display screen.
(3) Radiated vacuum ultraviolet ray has a long wavelength from the viewpoint of increasing energy conversion efficiency from vacuum ultraviolet ray to visible light.
(4) The discharge initiating voltage is low from the viewpoint of decreasing power consumption.
The rare gas includes He (wavelength of resonance line=58.4 nm), Ne (ditto=74.4 nm), Ar (ditto=107 nm), Kr (ditto=124 nm) and Xe (ditto=147 nm). While these rare gases may be used alone or as a mixture, mixed gases are particularly useful since a decrease in the discharge initiating voltage based on a Penning effect can be expected. Examples of the above mixed gases include Nexe2x80x94Ar mixed gases, Hexe2x80x94Xe mixed gases, Nexe2x80x94Xe mixed gases, Hexe2x80x94Kr mixed gases, Nexe2x80x94Kr mixed gases and Xexe2x80x94Kr mixed gases. Of these rare gases, Xe having the longest resonance line wavelength is suitable since it also radiates intense vacuum ultraviolet ray having a wavelength of 172 nm.
The light emission state of glow discharge in a discharge cell will be explained below with reference to FIGS. 21A, 21B, 22A and 22B. FIG. 21A schematically shows a light emission state when DC glow discharge is carried out in a discharge tube with a rare gas sealed therein. From a cathode to an anode, an Aston dark space A, a cathode glow B, a cathode dark space (Crookes dark space) C, negative glow D, a Faraday dark space E, a positive column F and anode glow G consecutively appear. In AC glow discharge, it is thought that since a cathode and an anode are repeatedly inverted at a predetermined frequency, the positive column F is positioned in a central area between the electrodes, and the Faraday dark spaces E, the negative glows D, the cathode dark spaces C, the cathode glows B and the Aston dark spaces A consecutively appear symmetrically on both sides of the positive column F. A state shown in FIG. 21B is observed when the distance between the electrodes is sufficiently large like a fluorescent lamp.
As the distance between the electrodes is decreased, the length of the positive column F decreases. When the distance between the electrodes is further decreased, presumably, the positive column F disappears, the negative glow D is positioned in the central area between the electrodes, and the cathode dark spaces C, the cathode glows B and the Aston dark spaces A appear symmetrically on both sides in this order as shown in FIG. 22A. The state shown in FIG. 22A is observed when the distance between the electrodes is approximately 1xc3x9710xe2x88x924 m. In the tri-electrode type plasma display device, the negative glow is formed in a space region near a surface portion of the dielectric material layer which portion covers one sustain electrode corresponding to the cathode or in a space region near a surface portion of the dielectric material layer which portion covers the other sustain electrode corresponding to the cathode.
When the distance between the electrodes comes to be less than 5xc3x9710xe2x88x925 m, presumably, the cathode glow B is positioned in the central area between the electrodes and the Aston dark spaces A appear on both sides of the cathode glow B as is schematically shown in FIG. 22B. In some cases, the negative glow can partly exist. In the tri-electrode type plasma display device, the cathode glow is formed in a space region near a surface portion of the dielectric material layer which portion covers one sustain electrode corresponding to the cathode or a space region near a surface portion of the dielectric material layer which portion covers the other sustain electrode corresponding to the cathode. When the distance between a pair of the sustain electrodes is arranged to be less than 5xc3x9710xe2x88x925 m as described above, and when the pressure in the space is adjusted to 1.0xc3x97102 Pa (0.001 atmospheric pressure) to 3.0xc3x97105 Pa (3 atmospheric pressures), the cathode glow can be used as a discharge mode. A high AC glow discharge efficiency can be therefore achieved, and as a result, a high light-emission efficiency and high brightness can be attained in the plasma display device.